1997 JET DT experiments revisited—comparative analysis of DD and DT stationary baseline discharges.

This paper compares the stationary ELMy H-mode baseline 50%–50% deuterium-tritium (DT) mixture discharges in the first high -power JET DT experimental campaign in 1997 (JET-DTE1) with the counterpart 100% deuterium (DD) baseline discharges which have the same engineering parameters, i.e. I_p, B_t, q₉₅, NBI power, plasma shape, no gas dosing, divertor structure, and the carbon wall. There is no difference in profile peaking of T_e, T_i, and n_e between the DT and the counterpart DD baseline discharges, indicating that there was no isotopic effect on the core transport in the stationary baseline DT discharges in the 1997 JET-DTE1. The core values of T_e, T_i, and n_e are higher in some DT discharges compared to their counterpart DD discharges, but this is attributed to the higher pedestal values, rather than any improvement in the core transport. The interpretive TRANSP simulations also show that the local heat diffusivity is not consistently different between the DT and the counterpart DD baseline discharges. The baseline discharges in the 1997 JET-DTE1 are also compared to the latest high-power ELMy H-mode baseline DD discharges with an ITER-like wall (ILW) in 2016. Despite the similar effective collisionality and ion heat deposition in the core, it was observed that T_i/T_e is consistently close to unity in the 1997 JET-DTE1 discharges, while the 2016 JET baseline discharges have high T_i, exceeding T_e, which enabled the highest fusion performance in the ITER-Like Wall. The high rotation frequency was the key factor in increasing T_i/T_e in the 2016 JET baseline discharges, and it is also the main difference compared to the stationary baseline discharges in the 1997 JET-DTE1. Based on this, it is prospected that higher rotation frequency is the key factor to achieving high fusion power in the stationary baseline discharges in the 2020 JET-DTE2, and the plasma operation with the low gas dosing and increased torque available in the present NBI system would enable such a high rotation frequency. [ABSTRACT FROM AUTHOR]